(a) Field of the Invention
The present invention is related to a precision screwdriver having a turning head, and more particularly, to one that allows the turning head to achieve agile rotation relatively to the handle of the screwdriver.
(b) Description of the Prior Art
Whereas, a precision screwdriver generally available in the market has its handle fixed or disposed with an interchangeable tip at a smaller end of the handle and is incorporated at another end of the handle with an axially pivoted handle. In use, one has his index finger to hold against the handle at the upper end of the handle and his thumb and another three fingers to hold the handle with the tip aiming at a screw with the handle as an axial to support rotation while rotating the handle by his thumb and other three fingers thus to turn and tighten or loosening the screw depending on the turning direction.
One of the prior art is essentially taking advantage of the space in the body of the handle to be incorporated with a retractable holder to receive and hold multiple exchangeable tips in position. Wherein, the rotation axle required in the use of the precision screwdriver is taken into consideration, and the space inside the handle is open to its end in a wider diameter to place the holder and ribs provided with locking troughs are longitudinally disposed in the middle section of the holder to clamp multiple tips. Both ends of those ribs are connected to define a circular shaft and a fender with the accommodation space in relation to the circular shaft having at its inner edge in the opening end to form protrusion wall and circular protrusion for temporary holding, and the extended end of the circular shaft in relation to the handle is provided to be engaged by a turning cap. Locking rings detachably pivoted to each other are respectively provided inside the cap and the circular shaft so to have the turning head functioning as a support axle for the handle of the screwdriver. By pulling the turning head, the protrusion wall clears away from the circular protrusion thus to consequently pull the holder out of the handle and the holder holds against the circular protrusion by the fender to all the exchange of the tips from the holder.
However, certain insufficiencies are observed from the prior art with their causes summarized as follows:
In use, one has his index finger to press the turning head while using his thumb and middle finger to turn the handle either to tighten up or loosening up the screw. Therefore when the handle rotates in relation to the turning head, the handle will cause the circular shaft to rotate relatively to the turning head. Since the circular shaft is connected to both of the turning head and the handle, a comparatively greater friction is created, resulting in that when the handle rotates in relation to the handle, the circular shaft and the holder at its bottom to turn at the same time. As multiple tips are caught in place on the holder making the total weight very heavy and the use of the screwdriver rather awkward when more strength is required to rotate the handle relative to the rotation by the turning head.